This game requires a NVIDIA GeForce 6 or ATI Radeon HD 2000 (R600) series graphics card or newer. In terms of the Linux software requirements, Frictional Games states that it needs a "Linux distribution released in 2010." The 155MB demo from the Helsingborg game studio can be found at AmnesiaGame.com. This game is powered by the HPL Engine 2, which they had developed in-house.
Below is the newest video trailer that has been released for Amnesia: The Dark Descent, which demonstrates the physics capabilities of this game.
The full version of this game is expected to be released next week.